When in a conducting state, thyristors remain in that state until the anode current drops below the holding current of the thyristor, at which point the thyristor commutates to the non-conducting or OFF state. One prior commutation technique employs the normal reversal of an AC current. Other known techniques include the discharge of a commutating capacitor into the thyristor to force the current to zero and the increase of the holding current of the thyristor by forcing a reverse gate current, as in the gate turn-off (GTO) thyristor. One method of reversing gate current in the GTO is called "emitter switching" or "cathode switching" and employs a switching device such as a mechanical switch or a transistor switch in series with the cathode of the GTO and a pair of diodes to conduct gate current around the switch when the switch turns off. The switch, in the ON state, must conduct the full GTO current and, in the OFF state, must support a relatively low voltage, typically in the order of 20 volts. The switch voltage drop in the ON state must be very low, on the order of 100 millivolts, in order to minimize energy loss. The purpose of this invention is to describe a thyristor commutation circuit with extremely low energy loss that is operated by means of a commutation circuit that is isolated from the thyristor circuit.